The potential for reformulating diesel fuel to reduce emissions is of considerable current interest. In 1993, the State of California established a reformulation program with emissions performance standards for diesel fuel in an effort to reduce emissions of NOx, PM and air toxics. More recently, the State of Texas proposed a similar diesel fuel program, and other states have considered such programs.
The attractiveness of diesel fuel reformulation to state authorities stems from the potential for achieving emissions reductions from the in-use vehicle fleet, predominantly heavy-duty diesel (HDD) engines. Other parties, including engine and vehicle manufacturers, may have interest in diesel fuel reformulation (beyond sulfur reductions) to enable new emission control technologies or to improve vehicle operating characteristics.
In response to the interest in diesel fuel reformulation, the U.S. Environmental Protection Agency (EPA) initiated a research effort to relate diesel fuel characteristics to HDD emissions. Relying on the compilation of emissions test data already published in the technical literature, the agency developed statistical models for exhaust emissions as functions of fuel properties such as aromatics content, specific gravity, and cetane number. The EPA work is summarized in two publications hereby incorporated in their entirety by reference: U.S. Environmental Protection Agency. 2001. Strategies and Issues in Correlating Diesel Fuel Properties with Emissions: Staff Discussion Document EPA420-P-01-001 (hereinafter “U.S. EPA 2001”) and Southwest Research Institute. July 2001. Diesel Fuel Impact Model Data Analysis Plan Review. SwRI 08.04075 (hereinafter “SwRI 2001”). This EPA work was presented at a public workshop in August 2001. Although recognized for contributions to the understanding of these issues, the results of the EPA effort evoked considerable discussion and some controversy in terms of statistical methodology, selection of variables, and model predictions. EPA subsequently concluded the work without adopting an approved statistical model of emissions for regulatory use.
Accordingly, a need in the art exists for reformulated diesel fuels for automotive diesel engines which meet the requirements of ASTM 975-02 and provide significantly reduced emissions of nitrogen oxides (NOx) and particulate matter (PM) relative to commercially available diesel fuels.